1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a program for providing a function of reducing noise of an image which is obtained from, for example, a camera array type image-capturing unit.
2. Description of the Related Art
In recent years, in an industry field, there is progressed high function formation of a camera which makes use of a concept of light field. Light field is a concept of dividing light which enters a lens from an object to capture an image thereof. There are two ways of main methods which embody the concept. A first one thereof is a method of arranging a lens array between a sensor and a main lens. A second one thereof is a method of a so-to-speak camera array (as known as camera array system, multiple lens camera, and the like) which uses plural sets of main lenses and sensors.
When a camera which makes use of the concept of light field is utilized, there can be realized a function which has not been present in a conventional single lens camera such as distance estimation, dynamic change of blur quality or the like. On the other hand, a performance of a conventional function can also be improved although the function is not new. For example, a performance of a noise reducing function can be improved.
Taking an example of the camera array, when a group of plural images obtained from the same object are aligned, and thereafter an average image of the images is generated, a noise is reduced in principle. For example, Japanese Patent Laid-Open No. 2011-113527 describes an invention in which images are aligned and superposed and a high-quality image is obtained by MAP method. Also, Japanese Patent Laid-Open No. 2011-022805 describes an invention of performing super-resolution processing by aligning.
However, in a system of averaging images by aligning as proposed in Japanese Patent Laid-Open No. 2011-113527 or Japanese Patent Laid-Open No. 2011-022805 described above, there is not provided a function of reducing noise in all of the areas in the image.
Because, occlusion is present in images which are captured from different view points, and there is present an image area which cannot be aligned. Occlusion signifies that there is generated an area an image of which can be captured by a certain image-capturing unit, but cannot be captured by other image-capturing unit. That is, although when an image area in which occlusion is not present, plural images can be aligned and thus noise is reduced, in an area in which the occlusion is present, plural images cannot be aligned and thus noise at a portion where images cannot be aligned cannot be reduced. In this way, there poses a problem that when noise of images which are captured from different view points is attempted to be reduced, a degree of reducing noise is changed depending on the image area.